2 minutes ago, P-47 Thunderbolt said:There is some wiggle room in that though.
I do generally agree with you, but it is sufficiently possible for there to be differences in ammo that it isn't quite that cut-and-dried. She does refer to them as being very rare, which I take to mean that you can't readily buy ammo for them anyway, so it is fairly likely that you'd have to seek out the same armorer who originally made you the weapon in order to get more ammo.
Armor piercing bullets are also pretty rare and hard to get, as are Hollow Point rounds, However, they're still manufactured to a standard size (.38 cal, .44 cal, 5.56 mm, 7.62 mm, etc). So, it wouldn't be the size of the projectile which is rare, but the specific type, such as what materials it is made from or special capabilities a particular round has beyond standard.